The present invention relates to a gas diffusion electrode which may be used in a fuel cell or electrochemical reactor or in electrolysis or electroplating processes.
A conventional gas diffusion electrode consists of a reaction layer and a gas diffusion layer joined with each other (e.g. see U.S. Pat. Nos. 4,931,168 and 4,748,095). The reaction layer consists of hydrophilic portions having fine passages through which a liquid can permeate; hydrophobic portions having fine passages through which a gas can pass, with the separate portions being mixed and contacted with each other; and a catalyst supported on the hydrophilic portions. The gas diffusion layer consists of hydrophobic portions containing fine passages through which a gas can pass. The gas diffusion electrode is utilized while an electrolyte is retained at the reaction layer side and a gas passes at the gas diffusion layer side.
If the interelectrode distance (the distance between an anode and a cathode) of the gas diffusion electrode is large, the electrical resistance increases such that the energy efficiency decreases. However, when the interelectrode distance is small, flow of the electrolyte is difficult to control thereby resulting in a decrease in energy efficiency.
An ion exchange membrane may be located between the electrodes, depending on the type of electrolysis process for which the gas diffusion electrode will be utilized. In the interelectrode distance is made smaller, then the distances between the ion exchange membrane and the electrodes are smaller, thereby decreasing the volume of the electrolyte flowing therebetween and resulting in decreased energy efficiency.